It seems RCT3 puts a very low priority on the thumbnail for park screenshots in the listing that displays in-game while we’re selecting which park to load.

In our experience, when viewing which park to open it will use the default thumbnail in that list until it decides it can spare the resources to load another.

Your park will usually need to run (not be in pause but run) for several minutes before the next save will have an updated thumbnail screenshot. It is not known if running the park in fast forward will reduce the amount of time this will take.

A new thumbnail is more likely to appear if we move the camera away from the location where it starts at in the park when the park is opened. Zooming in and out a few times seems to help ensure a new thumbnail.

If you’re running a huge busy park full tilt and flat out, if one saves every few minutes one will find that no matter how much you’ve moved around the park, that after about an hour the thumbnails for the park saves will stop updating and will all be the same. You may also find that if the game engine has for some reason dropped the thumbnail during this time, the park saves will show with a solid black thumbnail for every subsequent save until you exit the park and it is launched again.

If one is uploading a park to share with the community one can easily select the thumbnail of their choice with a previous version of Park CleanUp, v2.0.0. Once launched, simply select the option replace park preview picture.